Go to THE EXTENDED PERIODIC TABLE OF THE ELEMENTS for speculation on the elements in the "island of stability" theorists have proposed. I borrowed part of one image for the first panel---apologies to the original website and creators. They speculated that above atomic number 200, there probably are no stable elements---but since this is speculation without much evidence, I theorized, for story purposes, that there is another "island of stability" starting in the atomic number 220s.